1. Field of the Invention
The present invention generally relates to the temporary and permanent repair of components made from material such as plastics, glass, and other translucent or transparent materials. It is to be appreciated that the present invention has general and specific industrial application in the repair of various materials with preference to transparent and translucent materials.
Generally, polymers have the advantages of weight saving, high specific mechanical properties, and good corrosion resistance, which make them indispensable materials in all areas of manufacturing. Nevertheless, manufacturing costs are sometimes detrimental, since they can represent a considerable part of the total costs and are made even more costly by the inability to quickly and easily repair these materials without a complete, and expensive, total replacement. Furthermore, the production of complex shaped parts is still a challenge for the industry. The limited potential for complex shape forming offered by advanced materials leaves little scope for design freedom in order to improve mechanical performance and/or integrate supplementary functions. This has been one of the primary limitations for a wider use of advanced polymers and materials in cost-sensitive large volume applications. Additionally, the nature of these materials does not lend itself to easy repair, especially on cheap, mass-produced items and repair kits for more expensive, specialty items (such as in the aeronautical industry) which are bulky, expensive, and require a long time to complete the repair.
2. Description of Related Art
Shape memory polymers (SMP) and shape memory alloys (SMA) were first developed about 20 years ago and have been the subject of commercial development in the last 10 years. SMPs are polymers that derive their name from their inherent ability to return to their original “memorized” shape after undergoing a shape deformation. SMPs that have been preformed can be deformed to any desired shape below or above their glass transition temperature (Tg). If the SMP is below the Tg, this process is called cold deformation. When deformation of the SMP occurs above its Tg, the process is denoted as warm deformation. In either case the SMP must remain below, or be quenched to below, the Tg while maintained in the desired deformed shape to “lock” in the deformation. Once the deformation is locked in, the polymer network cannot return to a relaxed state due to thermal barriers. The SMP will hold its deformed shape indefinitely until it is heated above its Tg, whereat the SMP stored mechanical strain is released and the SMP returns to its preformed state.
SMPs are not simply elastomers, nor simply plastics. They exhibit characteristics of both materials, depending on their temperature. While rigid, an SMP demonstrates the strength-to-weight ratio of a rigid polymer; however, normal rigid polymers under thermal stimulus simply flow or melt into a random new shape, and they have no “memorized” shape to which they can return. While heated and pliable, an SMP has the flexibility of a high-quality, dynamic elastomer, tolerating up to 400% elongation or more; however, unlike normal elastomers, an SMP can be reshaped or returned quickly to its memorized shape and subsequently cooled into a rigid plastic. Most SMP can repeat this process at least several thousand times before losing its “shape memory effect.”
Several known polymer types exhibit shape memory properties. Probably the best known and best researched polymer types exhibiting shape memory polymer properties are polyurethane polymers. Gordon, Proc of First Intl. Conf. Shape Memory and Superelastic Tech., 115-120 (1994) and Tobushi et al., Proc of First Intl. Conf. Shape Memory and Superelastic Tech., 109-114 (1994) exemplify studies directed to properties and application of shape memory polyurethanes. Another known polymeric system, disclosed by Kagami et al., Macromol. Rapid Communication, 17, 539-543 (1996), is the class of copolymers of stearyl acrylate and acrylic acid or methyl acrylate. Other SMP polymers known in the art include articles formed of norbornene or dimethaneoctahydronapthalene homopolymers or copolymers, set forth in U.S. Pat. No. 4,831,094. Styrene copolymer-based SMPs are disclosed in U.S. Pat. No. 6,759,481 which is incorporated herein by reference. Additionally cyanate ester-based SMPs are disclosed in PCT Application PCT/US2005/015685 which is incorporated herein by reference.
Glass and plastics are used everywhere. When damage occurs to such materials, the normal repair method is a total replacement of the part. For example, parts which have suffered impact damage from a flying stone or other debris or from a dropped tool, a damage crater, crack, or hole often require total replacement as there are no current methods which provide adequate means of short or long-term repair and still provide a means for light to pass through the damaged part.
There are times when completely replacing a part is not satisfactory. This is due to the cost of replacement and the likelihood the replacement becoming damaged as well very soon after the repair. Additionally, depending on the part being repaired, it normally takes a long amount of time to remove, replace, and test the component, especially if the part is on an aircraft, automobile, or building.
Means of using resins and resin composites to repair parts are known in the art and these repair patches have been used both for repairing holes in drywall material as well as repairing holes in automobile bodies. U.S. Pat. No. 5,075,149 issued to Owens et al. (“Owens”), U.S. Pat. No. 4,707,391 issued to Hoffmann (“Hoffmann '391”) and U.S. Pat. No. 4,135,017 issued to Hoffmann (“Hoffmann '017”) are all directed to multi-layer repair patches.
Owens discloses a three-layered patch with a metal plate disclosed between two polyester sheets. The metal plate is held in place between the two polyester sheets with a semi-solid adhesive such as urethane. The semi-solid adhesive fixedly attaches the two polyester sheets together as well as fixedly attaching the reinforcing metal plate between the two sheets. Owens is not useful for repairs which require the application of bonding material or plaster to the repair patch because the bonding material or plaster cannot readily pass through the mesh due to the presence of the urethane adhesive. Additionally the patch cannot be molded quickly, on-site, without additional time and equipment. Finally, the patch described in Owens does not allow for the repair of a transparent or translucent part while simultaneously allowing light to pass through the repair.
Hoffmann '391 discloses a two-layer patch including a perforated metal plate with an outer fiberglass mesh attached to one side of the plate. A glue or adhesive coating is applied to the surface of the plate that is attached to the surface to be repaired and an additional adhesive coating is applied to the inward-facing surface of the fiberglass mesh to attach the mesh to the metal plate as well as to attach the mesh to the surface under repair.
Hoffmann '017 also discloses a two-layer patch. An inner metal plate is covered with adhesive that secures one surface of the plate to the surface under repair. An outer plate cover is laminated onto the exterior side of the metal plate by means of a layer of adhesive applied to the inward-facing side of the plate cover.
Both of these methods employ metal plates in the final patch with limits the ability of these patches to be easily and quickly molded to the damaged part on-site. Additionally, the use of metal eliminates some of the weight saving advantages of a pure composite repair patch. Finally, the patches described in Hoffmann '391 and '017 do not allow for the repair of a transparent or translucent part while simultaneously allowing light to pass through the repair.
Additionally, the repairs alone in these methods can take anywhere from 15-20 minutes to several hours depending on the part or parts to be replaced and the location and size of the part to be replaced. Additionally, the added expense for replacing the part immediately can make the replacement cost significantly more than what was originally planned.
Additionally, if mass-produced items, such as car lights, windshields, windows and other similar manufactured parts are damaged, it is oftentimes less expensive to replace the entire part than to repair it, although such parts are often expensive themselves. Thus, there is a need for a cheap, quick, and effective method of repairing such mass-produced parts and for quickly and reliably repairing other high-end parts.
It is the object of the present invention to provide a preformed and cured patch and a method to quickly and cheaply permanently repair any number of items with a transparent or translucent material which retains similar or greater mechanical properties of the parts repaired. This and other objects of the present invention wilt become apparent from the following specification.